RFR: 8258422: Cleanup unnecessary null comparison before instanceof check in java.base [v3]

[Andrey Turbanov]

> 8258422: Cleanup unnecessary null comparison before instanceof check in java.base

Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:

  8258422: Cleanup unnecessary null comparison before instanceof check in java.base
  use instanceof pattern matching in UnixPath too

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/20/files
  - new: https://git.openjdk.java.net/jdk/pull/20/files/603cd364..0d2ac405

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=20&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=20&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/20.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/20/head:pull/20

PR: https://git.openjdk.java.net/jdk/pull/20